Why did my dog suddenly attack my other dog

Picture this: your two retrievers who've peacefully shared your Seattle apartment for years suddenly erupt in a snarling tangle over a dropped blueberry. For new multi-dog households, these unexpected fights feel like betrayal - but sudden aggression rarely comes without warning. The key lies in spotting hidden triggers. Unlike predatory behavior, conflict between familiar dogs often stems from resource stress (that high-value chew bone), pain-induced irritability (your senior Lab's arthritis flare-up), or social tension (shifting pack dynamics after a kennel stay). Take Bailey and Charlie in Chicago: their fights began after construction noise disrupted sleep cycles, leaving both dogs on hair-trigger alert. Their previously stable relationship shattered overnight.

Scientifically, sudden aggression frequently links to undiagnosed medical issues. Pain from dental abscesses, hypothyroidism, or UTIs can make even gentle dogs lash out - your 8-year-old Shepherd snapping when jumped on might be guarding a sore hip. Hormonal shifts or fading eyesight also contribute. This is why step one is always a full veterinary workup (including updated rabies vaccines, legally required nationwide). Neurologically, "trigger stacking" explains explosions: a delivery truck scare + territorial marking at the door + interrupted nap = fight over a water bowl. Punishing warning growls worsens this; suppressed signals lead to unpredictable attacks that violate animal welfare standards.

Practical management starts with immediate separation using baby gates - not punishment. Create visual barriers in your apartment so dogs can decompress. Next, implement "nothing in life is free": both dogs must sit before meals, doors open, or affection given. This rebuilds respect without confrontation. For resource guarding, feed in separate rooms and pick up toys. Use positive reinforcement when calm: "Yes!" + treat when they relax near each other. Apartment dwellers should rotate walks to prevent leash tension building indoors. During flare-ups, interrupt with a sharp "hey!" or shaken penny can - never physical intervention. Track incidents in a journal: time, location, and preceding events reveal patterns.

Responsible resolution honors community safety. Always leash dogs separately during walks (many cities fine for multi-dog leashing), and carry triple the biodegradable bags - stress-induced accidents happen. Notify neighbors about training; a simple note explaining "we're working with a behaviorist" prevents noise complaints in thin-walled buildings. Culturally, avoid dominance theories like alpha rolls - banned in several states and proven to escalate aggression. Instead, hire IAABC-certified professionals for desensitization protocols. Remember: unaddressed aggression risks legal consequences under dangerous dog ordinances, especially if injuries occur. With patience and science-backed methods, most dogs relearn peaceful coexistence within 2-6 months, transforming your home back into a sanctuary.